The crisp new dollar bill that I have just taken from my wallet bears the serial number 24598176. It’s easy to tell that the number is exactly divisible by 2 but not by 5. Is it divisible by 3? by 4?

It’s easy to tell if a given whole number is divisible by 2. Just check whether the last digit is even. There are also simple rules to determine whether a number is ...

Prime numbers, vital in mathematics and competitive exams, can be quickly identified using a systematic approach. This method involves checking divisibility by primes up to the square root of the ...